1. Field of the Invention
The invention relates to a filament winding method and a filament winding apparatus, by which filament such as ceramic fiber, glass fiber, and carbon fiber is unwound from a bobbin upon which the filament is wound.
2. Description of Related Art
In recent years, a method for forming a reinforcing fiber preform has been widely used, in which filament made by impregnating ceramic fiber, glass fiber, carbon fiber, or the like into a resin or the like is unwound at certain tension from a bobbin upon which the filament is wound, and the unwound filament is wound on an object to be wound upon. Also, a filament winding apparatus is used as an apparatus for unwinding the filament from the bobbin at certain tension. For example, as shown in FIG. 5, Japanese Patent Application Publication No. 2005-262595 (JP 2005-262595 A) discloses a filament winding apparatus 100 including a bobbin moving mechanism 170 that is able to change relative positions of a bobbin 110 and a guide roller 141, and the filament winding apparatus 100 is able to maintain certain tension of unwound filament adequately even when the filament is unwound at high speed. In FIG. 5, reference numerals 141 to 146 denote guide rollers. Control means 160 controls an active dancer device 130A having an active dancer unit 151 and a dancer 130 based on detection signals from a tension sensor 140A and a speed sensor 140B to maintain the certain tension of the unwound filament, and controls the bobbin moving mechanism 170 to move the bobbin 110 to an appropriate position in an axis direction. Also, for example, Japanese Patent Application Publication No. 2007-161449 (JP 2007-161449 A) discloses a thread winding apparatus and a thread winding method by which a thread is wound on a bobbin. For detail, a thread winding apparatus and a thread winding method are disclosed, in which rotation speed of a package driving motor for driving a bobbin to rotate is changed between before and after a diameter of the bobbin, which has wound up a thread, reaches a given limit diameter. Thus, a single wind ratio is maintained from start to end of winding. A diameter of a point of the thread wound on the bobbin is detected by winding bobbin diameter detecting means that detects an oscillation angle of a cradle that holds the bobbin.